Advanced austenitic stainless steels are a group of austenitic stainless steels with a Ni content near or higher than 30 wt% and a pitting resistance equivalent number (PRE value) higher than 40 [1]. They have been used in the areas with the special demands such as oil-gas, petrochemical and chemical industries. Due to high amount of Ni in the alloys, they are relatively expensive. On the other hand, with the exploitation of the deeper oil wells, the materials with better performances are required [2]. In this work, new advanced austenitic stainless steels with higher strength, elongation and corrosion resistance were developed using a new concept of deformation twinning and addition of nitrogen. With a combination of the ab initio modelling and experimental work, the results show that addition of nitrogen may increase the stacking fault energy of the steel that makes the difficulty for deformation twinning by a higher critical stress. However, it can also significantly increase its strain strengthening rate and consequently the flow stress. This can cause the occurrence of deformation twinning at a smaller strain and leads to a higher ductility or elongation.

The new advanced austenitic stainless steels also show a TWIP behaviour with an elongation higher than 80% and a tensile strength higher than 1000 MPa at cryogenic temperature (-196°C). The magnetic entropy of the material is another factor that affects the deformation twinning. The influence of nitrogen addition on the magnetic property and its effect on deformation twinning are also discussed. The present work increases the understanding for the development of advanced austenitic stainless steels with high performance and low cost. 

References 
[1] P. Kangus, G. Chai, Adv. Mater. Res. 2013, 794, 645.
[2] B. Craig, ADVANCED MATERIALS & PROCESSES/MAY 2008, 33-3